A computer network generally consists of a plurality of networked devices physically connected to each other through some communication medium, such as a copper or fiber optic cable. Networked devices typically include, for example, computer workstations, hubs or concentrators, and routers. As networks become increasingly complex, it becomes increasingly important to keep track of the various networked devices on a network, and how they are interconnected. Such interconnection information is referred to herein as the topology of the network.
In the past, a strategy has been developed for constructing the topology of a network based on databases maintained on each of the concentrators in the network. According to this strategy, certain devices ("ID-transmitting devices") such as concentrators, are configured to periodically generate identification signals. Each identification signal contains information identifying the D-transmitting device which originally generated the identification signal. When a concentrator receives an identification signal, a medium access controller ("MAC") in the concentrator stores data indicating (1) the D-transmitting device from which the identification signal originated, and (2) the specific slot and port on which the identification signal was received. The MAC stores this information in a database (a "ID/port database") on the concentrator.
The concentrator rebroadcasts the identification signals it receives, and its own identification signals, to all other concentrators on the network, which build their own ID/PORT databases. A network management station on the network periodically polls each concentrator to access the information contained in the various ID/PORT databases, and from this information constructs a database of the topology of the network. One example of this topology construction strategy is described in U.S. Pat. No. 5,226,120 issued to Brown et al. on Jul. 6, 1993.
The above-described strategy works well as long as each concentrator is able to monitor all of the identification signals it receives, and is able to send its own identification signals over all of the channels to which it is connected. A MAC can only monitor incoming identification signals on a single communication channel at a time. Therefore, as long as each concentrator contained only one communication channel, concentrators needed only one MAC to implement the above-described strategy.
However, concentrators have now been developed which support more than one communication channel. Such multiple-channel concentrators are superior to single channel models in that each communication channel may support an entirely separate network. While a MAC is monitoring and maintaining a database for the identification signals received over one communication channel in a given concentrator, identification signals received over all other communication channels in the given concentrator go unmonitored and unrecorded.
One way to guaranty that identification signals from all ID-transmitting devices connected to a multiple-channel concentrator are monitored and recorded, and to insure that a multiple-channel concentrator transmits its own identification signals over each channel to which it is connected, is to design the multiple-channel concentrator with one MAC per channel. Each channel would be monitored by its respective MAC, and each MAC would record the identification signals received over its respective channel in a central ID/PORT database. Each MAC would also transmit the concentrator's identification signals over its respective channel.
Unfortunately, the incorporation of multiple MACs into a single concentrator may significantly increase the price and complexity of the concentrator. Therefore, it is clearly desirable to provide a multiple-channel concentrator with a single MAC capable of accurately maintaining an ID/PORT database which reflects all of the ID-transmitting devices physically connected to a multiple-channel concentrator. In addition, it is desirable that the single MAC be capable of transmitting identification signals for the multiple-channel concentrator over all of the channels to which the concentrator is connected so that other concentrators may accurately maintain their own ID/PORT databases.